This new rapid-assembly ferrule-less connector concept can change the economics of liquid or gas applications demanding high integrity and/or higher pressure operation.
The selection of fitting technology depends on pressures, temperatures and media. However, when applications demand very high reliability, or involve pressures beyond the scope of other industry-standard fittings, choice becomes limited and the cost of the fitting itself can be a tiny fraction compared to the cost of installation. This is especially the case with many marine, oil and gas applications in hydraulic lines, services and instrumentation.
This is the application focus of a new type of tube connector system for permanent connections, Phastite. Designed primarily as an alternative to welded tube fittings, the technology introduces a unique, patented method of sealing with four raised compression ‘rings’ that grip the tubing and ensure 100% leak-tight performance every time - providing the means to reduce assembly times by up to 100 fold (see photo).
Photo 1: Phastite fittings bring simplified assembly to permanent-connection and high-pressure applications currently served by welded technologies.
Offshore oil and gas applications are an important focus, and during development the fitting has been subjected to a number of tests to demonstrate its effectiveness. These include simulating pressures at depths of over 20,000 feet.
The fitting is available for tube outside diameter sizes up to 1 inch/25 mm, and is designed to withstand working pressures up to 1,379 bar (20,000 PSI). In the oil and gas sector, a wide variety of applications fall within this category, ranging from pump-driven high-pressure hydraulics, through deep-water oil and gas drilling operations, to vessels and even subsea equipment.
Before looking at the tube fitting, it's worth reviewing currently available alternatives and the problems they face. Here, we are talking of rigid steel tubing which involves stainless steel fittings in the so-called 'medium pressure' region, working generally up to around 1,000 bar / 15,000 PSI.
In general, twin-ferrule fittings with the simple and familiar compression-assembly principle ('one and quarter turns' to assemble) can be specified for pressures up to 15,000 PSI depending on the tubing size selected. Not withstanding this, many users will restrict such fittings to a 6,000 PSI maximum. Beyond this point, other fitting technologies are typically used, usually welded, or cone-and-thread.
When welded connections are used, it's for long-term permanency. Effectively, when the fittings are in the same material as the tubing, they become an integral part of the system. Although the aim is laudable, there is a considerable price to be paid in terms of the worker skill and equipment required, and the time to fabricate each joint. Installers of welded fittings also face extra difficulties. When working on oil and gas platforms, ‘hot work' permits are usually needed, involving administration and safety procedure work, all of which adds to the cost of the field work. If testing is required using dye penetrant or X-ray techniques, as it can be for high reliability applications, then the costs can escalate substantially.
What the Phastite fitting sets out to achieve is to reduce assembly time considerably. A compact hydraulically operated tool, which accompanies the fittings, enables this (photo). In the offshore field in particular, this approach allows fittings to be positioned closely against panels, thus avoiding having to bend the tubing to engage the tool.
Photo 2: Phastite tooling allows assembly direct against panels and bulkheads.
After sliding each tube end into the fitting, the loose assembly is then placed in the tooling. The tooling applies hydraulic pressure to the collar(s) of the fitting. As the collars are moved inwards they force the profiles of the internal sleeve to grip the tubing, thus providing a high-pressure, leak-tight seal. Installation is complete when a metal-to-metal dead stop of the collars is reached.
The designed-for-purpose nature of the tool assures users of correct, right-first-time assembly (with other tube fitting systems, a degree of rework is almost always required). The assembly time itself is measured in seconds, and requires no consumables. This can dramatically reduce the operations and costs compared with welded fittings.
Phastite's sealing mechanism is based on a series of raised compression rings that create a compression seal (visible in photo 1) without weakening the tubing surface. The compression rings effectively grip in a way that retains all of the tubing's strength.
These profiles also make the fitting particularly suitable for vibration prone environments. In testing to verify conformance with BS 4368 for example (which calls for 20 million vibration cycles at between 23 and 47 Hz - some 238 hours of testing in total), Phastite fittings were left on the rig until destruction. The fittings still retained their seal even in excess of 400 hours, and at this point, the test frequency was increased way beyond the range of the standard, and the fittings continued to operate for another 40 hours.
An additional point to consider in terms of cost is the ability to use thinner wall tubing on gas services, due to Phastite’s multiple profiles providing excellent sealing without any detrimental effect on the tubing.
Learn more about this innovative tube connector system from Parker:
Article contributed by Instrumentation Products Division Europe, Parker Hannifin.
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